Prop selection for a 21' Larson with 4.3l

rock doc

Petty Officer 1st Class
Joined
May 29, 2011
Messages
241
I may have found a good used prop (Stainless Steel Prop Quicksilver Laser 2 19' Pitch #48-16544-19) fro $200 and wondering if it is in the right ballpark for my boat. Here are the specs on my boat:

Year: 1990
Length: 21' with cuddy
Width: 99"
Weight: 2850 pounds with an empty fuel tank and without any gear or passengers
Engine: 175hp 4.3l merc with alpha 1
Current Prop: three blade aluminum 19"

I'll go check the prop diameter tomorrow and see what the gearing is on the drive. The current aluminum prop is a little out of shape, but at WOT the boat will run 40mph at 4400rpm. I'll make sure I have a handheld GPS this weekend to verify the speed. I'm hoping he'll let me return the prop if if doesn't work on my boat.


I like to pull tube and intermediate level skiing (slalom). The prop currently pulls a skier resonantly well considering the boat and motor combo. There seems to be some conflicting information out there on whether changing to ss will increase or decrease the rpms. I suspect that the amount cupping may explain some of this.

Is the Quicksilver Laser II intended for this type of usage or is it more of a high speed prop intended for performance boats?

Any advice would be appreciated. Perhaps I should go with a different setup all together...maybe one of those hubs with changeable blades. We are fortunate enough to live a a very large water way and sometimes cruise 8-10 hrs to overnight.
 

jestor68

Commander
Joined
Jun 12, 2012
Messages
2,308
Re: Prop selection for a 21' Larson with 4.3l

Not really. The Laser is intended for bass boats and high performance type hulls where the motor is raised higher than "normal".

If you are only getting 4400 rpm now it would load the motor even more. By the way, your motor's WOT rpm range is 4400-4800 rpm.

A Solas Amita 15-1/2 X 17 would put you right at 4700-4800 rpm and provide very good acceleration for water sports. It's necessary to order the Solas thrust washer with the prop. $117.99 + $14.08.
 

rock doc

Petty Officer 1st Class
Joined
May 29, 2011
Messages
241
Re: Prop selection for a 21' Larson with 4.3l

Perfect...thanks for the advice. I may even try purchasing a hub and blade system so I can switch back and forth for skiing and cruising.
 
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